The radial combination weighing machine with a nutating distribution disc is an improvement upon the combination weighing machines of the type generally described and claimed in commonly owned U.S. Pat. Nos. 4,630,695 and 4,901,807, the specifications and drawings of which are incorporated herein by reference.
When using a combination weighing machine of the type disclosed in the above referred to U.S. Pat. Nos. 4,630,695 and 4,901,807, a target package weight is preselected. Fractional amounts of the target package weight, which shall be referred to as product batches, are metered through a plurality of product batch handling units. Each separate product batch handling unit includes, in addition to other components, a radially extending product feeder trough, an accumulation chamber and a weighing device. The weighing device weighs the product batch that has been metered to it and records the weight; the weighed product batch is stored either in a weigh bucket associated with the weighing device or in a holding chamber disposed therebelow.
The weight of the product batches that are metered to the weighing devices can be controlled, for example by controlling the feed time for the conveying mechanism that meters out the product batches. When a complete set of product batches has been weighed, recorded and stored then the total weights for all combinations that can be formed using all available product batches is calculated and compared to the target package weight. A best combination that is equal to or within a predetermined range of the target package weight is selected. After the product discharge has been completed the selected holding chambers are discharged into a collection chamber for the formation of a package, the discharged holding chambers are then replenished and the cycle of selecting another best combination is repeated.
The likelihood of achieving an acceptable combination increases as the number of product batches used to fulfill the target package weight increases and as the number of holding chambers available to choose from increases. The latter of these two variables is fixed for a given machine and thus fine tuning of the system usually involves adjustments to the weight of the fractional amounts. For example if the target package weight is six (6) ounces, the product batches are about two (2) ounces and there are eight (8) holding chambers available to choose from, then the likelihood of achieving an acceptable combination would be increased by reducing the weight of the product batches to about one-and-one-half (11/2) ounces.
The prior art combination weighing machines are of two types, in-line and radial. The in-line type machines have the weighing devices arranged side by side. The radial type machines have the weighing devices spaced around a circle. As disclosed in the above identified U.S. Pat. Nos. 4,630,695 and 4,901,807, a single weighing device, which is the most expensive component of the combination weighing machine, can function to weigh product for multiple holding chambers, thus decreasing the per holding chamber cost of the machine. This can be accomplished, for example, by feeding the product from the weighing device through a diverter that functions to direct the product to one or another of the associated holding chambers.
In radial weighing machines a product source can deposit bulk product on a stationary conical disc located at the center of the circle around which the weighing devices are located. The product flows radially outwardly along the upper surface of the stationary conical disc. The product discharges from the stationary conical disc into radially extending feeder troughs that can be driven, for example, by a vibratory drive for discharge into an accumulation chamber. A drive such as this is disclosed in the U.S. Pat. No. 3,108,647 to Harmon et al. In Harmon et al, this type of drive was used for topping off the weighing buckets, but could have been used in radial combination weighing machine such as are disclosed in FIGS. 5 and 6 of the above referred to U.S. Pat. No. 4,901,807. A distribution table formed of a stationary conical disc imparts only radial movement to the product, which is the desired directional movement for the product. However, some products stick to the stationary conical disc and thus do not feed consistently with such a system. To remedy this, power means can be provided to impart rotational or spiral reciprocating vibratory motion to the distribution disc. Drives such as this have the disadvantage that they impart an undesirable circumferential direction of motion to the product as it is discharged from the distribution disc to the radial troughs. This not only unnecessarily increases the power requirements, imparts an undesirable direction of movement to the product but can also result in product missing the radial troughs and being wasted.
It is a primary objective of the present invention to provide a distribution disc that imparts motion to the product that has been deposited thereon causing the product to move in the radial direction.
Another objective of the present invention is to provide a distribution disc that nutates to create a feed action to product deposited on the distribution disc of varying amplitude.
Still another objective of the present invention is to provide a radial combination weighing machine with a nutating distribution disc that imparts motion to product that has been deposited thereon only in the radial direction.
Yet another objective of the present invention is to provide a radial combination weighing machine with a dynamically balanced nutating drive for the distribution disc that will not introduce undesirable vibrations into the machine.